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National Cancer Institute Fact Sheet
    Reviewed: 03/17/2008
Tamoxifen: Questions and Answers

Key Points
  1. What is tamoxifen?

    Tamoxifen (Nolvadex®) is a drug, taken orally as a tablet, which interferes with the activity of estrogen, a female hormone. Estrogen can promote the development of cancer in the breast. Tamoxifen is approved by the U.S. Food and Drug Administration (FDA) for the prevention of breast cancer and for the treatment of breast cancer, as well as other types of cancer.

    Tamoxifen has been used for more than 30 years to treat breast cancer in women and men. Tamoxifen is used to treat patients with early-stage breast cancer, as well as those with metastatic breast cancer (cancer that has spread to other parts of the body). As adjuvant therapy (treatment given after the primary treatment to increase the chances of a cure), tamoxifen helps prevent the original breast cancer from returning and also helps prevent the development of new cancers in the other breast. As treatment for metastatic breast cancer, the drug slows or stops the growth of cancer cells that are present in the body.

    Tamoxifen has been used for almost 10 years to reduce the risk of breast cancer in women who are at increased risk of developing breast cancer. Tamoxifen is also used to treat women with ductal carcinoma in situ (DCIS), a noninvasive condition that sometimes leads to invasive breast cancer.

  2. How does tamoxifen work?

    Estrogen can promote the growth of breast cancer cells. Some breast cancers are classified as estrogen receptor-positive (also known as hormone sensitive), which means that they have a protein to which estrogen will bind. These breast cancer cells need estrogen to grow. Tamoxifen works against the effects of estrogen on these cells. It is often called an antiestrogen or a SERM (Selective Estrogen Receptor Modulator).

    Studies have shown that tamoxifen is only effective in treating estrogen receptor-positive breast cancers. Therefore, the tumor’s hormone receptor status should be determined before deciding on treatment options for breast cancer.

    Although tamoxifen acts against the effects of estrogen in breast tissue, it acts like estrogen in other tissue. This means that women who take tamoxifen may derive many of the beneficial effects of menopausal estrogen replacement therapy, such as a decreased risk of osteoporosis.

  3. How long should a patient take tamoxifen for the treatment of breast cancer?

    Patients with metastatic breast cancer may take tamoxifen for varying lengths of time, depending on the cancer’s response to this treatment and other factors. When used as adjuvant therapy for early-stage breast cancer, tamoxifen is generally prescribed for 5 years. However, the ideal length of treatment with tamoxifen is not known.

    Two studies have confirmed the benefit of taking adjuvant tamoxifen daily for 5 years. When taken for 5 years, tamoxifen reduces the chance of the original breast cancer coming back in the same breast or elsewhere. It also reduces the risk of developing a second primary cancer in the other breast.

    Clinical trials are ongoing to determine whether hormone therapy taken for more than 5 years is beneficial. These studies usually include aromatase inhibitors (AIs) (another type of antiestrogen) (see Question 15). For example, the National Cancer Institute (NCI), a part of the National Institutes of Health, is sponsoring the National Surgical Adjuvant Breast and Bowel Project (NSABP) B–42 trial. This trial is studying the AI letrozole (Femara®) to find out how well it works compared with a placebo in treating postmenopausal women who have received hormone therapy for hormone receptor-positive breast cancer. More information is available in PDQ®, the NCI’s comprehensive cancer information database, at http://www.cancer.gov/clinicaltrials/NSABP-B-42 on the Internet.

    The MA–17R trial, which is being coordinated by the National Cancer Institute of Canada’s Clinical Trials Group, is comparing letrozole with placebo in women previously diagnosed with primary breast cancer who participated in another clinical trial of letrozole. Information about the MA–17R trial can be found at https://www.swogstat.org/ROS/ROSBooks/Fall%202006/Intergroup/NCIC%20CTG/JMA17R.pdf on the Internet.

  4. What are some of the more common side effects of tamoxifen?

    The known, serious side effects of tamoxifen are blood clots, strokes, uterine cancer, and cataracts (see Questions 5–8). Other side effects of tamoxifen are similar to the symptoms of menopause. The most common side effects are hot flashes and vaginal discharge. Some women experience irregular menstrual periods, headaches, fatigue, nausea and/or vomiting, vaginal dryness or itching, irritation of the skin around the vagina, and skin rash. As with menopause, not all women who take tamoxifen have these symptoms. Men who take tamoxifen may experience headaches, nausea and/or vomiting, skin rash, impotence, or a decrease in sexual interest.

  5. Does tamoxifen cause blood clots or stroke?

    Data from large clinical trials suggest that there is a small increase in the number of blood clots in women taking tamoxifen, particularly in women who are receiving anticancer drugs (chemotherapy) along with tamoxifen. The total number of women who have experienced this side effect is small. The risk of having a blood clot due to tamoxifen is similar to the risk of a blood clot when taking estrogen replacement therapy.

    The Breast Cancer Prevention Trial (BCPT), a large research study funded by the NCI, was designed to test the usefulness of tamoxifen in preventing breast cancer in women with an increased risk of developing this disease (see Question 12). This study also found that women who took tamoxifen had an increased chance of developing blood clots and an increased chance of stroke (1, 2).

  6. Does tamoxifen cause cancers of the uterus?

    Tamoxifen increases the risk of two types of cancer that can develop in the uterus: endometrial cancer, which arises in the lining of the uterus, and uterine sarcoma, which arises in the muscular wall of the uterus. Like all cancers, endometrial cancer and uterine sarcoma are potentially life-threatening. Women who have had a hysterectomy (surgery to remove the uterus) and are taking tamoxifen are not at increased risk for these cancers.

    Endometrial Cancer
    Studies have found the risk of developing endometrial cancer to be about 2 cases per 1,000 women taking tamoxifen each year compared with 1 case per 1,000 women taking placebo (1, 2). Most of the endometrial cancers that have occurred in women taking tamoxifen have been found in the early stages, and treatment has usually been effective. However, for some breast cancer patients who developed endometrial cancer while taking tamoxifen, the disease was life-threatening.

    Uterine Sarcoma
    Studies have found the risk of developing uterine sarcoma to be slightly higher in women taking tamoxifen compared with women taking placebo. However, it was less than 1 case per 1,000 women per year in both groups (1, 2). Research to date indicates that uterine sarcoma is more likely to be diagnosed at later stages than endometrial cancer, and may therefore be harder to control and more
    life-threatening than endometrial cancer.

    Abnormal vaginal bleeding and lower abdominal (pelvic) pain are symptoms of cancers of the uterus. Women who are taking tamoxifen should talk with their doctor about having regular pelvic examinations and should be checked promptly if they have any abnormal vaginal bleeding or pelvic pain between scheduled exams.

  7. Does tamoxifen cause other types of cancer?

    Tamoxifen is not known to cause any types of cancer in humans other than endometrial cancer and uterine sarcoma.

  8. Does tamoxifen cause eye problems?

    As women age, they are more likely to develop cataracts (clouding of the lens inside the eye). Women taking tamoxifen appear to be at increased risk for developing cataracts. Other eye problems, such as corneal scarring or retinal changes, have been reported in a few patients.

  9. Should women taking tamoxifen avoid pregnancy?

    Yes. Doctors advise women receiving tamoxifen to avoid pregnancy because animal studies have suggested that the use of tamoxifen during pregnancy can cause harm to the fetus. Women who have questions about fertility, birth control, or pregnancy should discuss their concerns with their doctor.

  10. Does tamoxifen cause a woman to begin menopause?

    Tamoxifen does not cause a woman to begin menopause, although it can cause some symptoms that are similar to those that may occur during menopause. In most premenopausal women taking tamoxifen, the ovaries continue to act normally and produce estrogen in the same or slightly increased amounts.

  11. Do the benefits of tamoxifen in treating breast cancer outweigh its risks?

    The benefits of tamoxifen as a treatment for breast cancer are firmly established and far outweigh the potential risks. Patients who are concerned about the risks and benefits of tamoxifen or any other medications are encouraged to discuss these concerns with their doctor.

  12. Can tamoxifen prevent breast cancer?

    Research has shown that when tamoxifen is used as adjuvant therapy for early-stage breast cancer, it reduces the chance that the original breast cancer will come back in the same breast or elsewhere. It also reduces the risk of developing new cancers in the other breast. Based on these findings, the NCI funded the BCPT to determine whether taking tamoxifen for at least 5 years can prevent breast cancer in women who have never been diagnosed with breast cancer but who are at increased risk of developing the disease. This study found a reduction in diagnoses of invasive breast cancer among women who took tamoxifen for 5 years. Women who took tamoxifen also had fewer diagnoses of noninvasive breast tumors, such as DCIS or lobular carcinoma in situ (LCIS) (1). After 7 years of follow-up, researchers found similar results (2). The study found that tamoxifen reduced the occurrence of estrogen receptor-positive tumors by 69 percent, but no difference in the occurrence of estrogen receptor-negative tumors was seen (1). More information about the BCPT is available on the NCI’s BCPT home page at http://www.cancer.gov/clinicaltrials/digestpage/BCPT on the Internet.

  13. Who should take tamoxifen to reduce breast cancer risk?

    The decision to take tamoxifen is an individual one. A woman and her doctor must carefully consider the benefits and risks of therapy. At this time, there is no evidence that tamoxifen has a net benefit for women who do not have an increased risk of developing breast cancer.

  14. What is raloxifene and how does it compare to tamoxifen?

    Raloxifene is a drug approved by the FDA for the prevention and treatment of osteoporosis in postmenopausal women. Raloxifene is also approved by the FDA for reducing the risk of invasive breast cancer in postmenopausal women with osteoporosis and in postmenopausal women at high risk for invasive breast cancer.

    The NCI funded the Study of Tamoxifen and Raloxifene (STAR), a clinical trial comparing raloxifene (Evista®) with tamoxifen in preventing breast cancer in postmenopausal women who are at an increased risk of developing the disease. The study found that raloxifene and tamoxifen are equally effective in reducing invasive breast cancer risk in postmenopausal women who are at increased risk of the disease. The study also found that women who took raloxifene had fewer uterine cancers and fewer blood clots than the women who took tamoxifen (3). However, raloxifene did not reduce the risk of noninvasive breast tumors such as DCIS and LCIS (3). Other side effects associated with raloxifene were similar to tamoxifen and included hot flashes, vaginal dryness, joint pain, and leg cramps. Studies of raloxifene to date have only examined its role in breast cancer prevention, not treatment.

    More information about STAR is available on the NCI’s STAR home page at http://www.cancer.gov/star on the Internet.

  15. What other hormone therapy may be used for early-stage breast cancer?

    Aromatase inhibitors (AIs) are another adjuvant treatment option for some women with early-stage breast cancer. AIs block the action of a protein called aromatase, which helps the body produce estrogen. Most of the estrogen in a woman’s body is made in the ovaries, but other tissues can also produce this hormone. AIs are usually used in women who have reached menopause, when the ovaries are no longer producing estrogen.

    Although AIs and tamoxifen both help to prevent the growth of estrogen-sensitive breast tumors, they work differently in the body. Tamoxifen blocks the tumor’s ability to use estrogen, and AIs reduce the amount of estrogen in the body. Anastrozole (Arimidex®), exemestane (Aromasin®), and letrozole (Femara®) are AIs that have been approved by the FDA.

    The American Society of Clinical Oncology (ASCO) recommends that postmenopausal women with hormone-sensitive breast cancer consider one of two adjuvant treatment options (4):

    • Begin treatment with tamoxifen for 2 to 3 years or 5 years, and then switch to an AI for another 2 to 3 years or 5 years.
    • Forego tamoxifen entirely and begin adjuvant treatment with an AI for 5 years.

    ASCO concluded that AIs are appropriate as initial treatment for women who should not take tamoxifen and that patients who cannot take AIs should receive tamoxifen.

    Whether an individual patient should start therapy with an AI or begin therapy with tamoxifen and then change to an AI is a subject of medical judgment and clinical research. Patients should talk with their doctors about which drug would be best for them given their particular medical situation.

    Question 3 includes information about ongoing clinical trials involving AIs to treat postmenopausal women with hormone receptor-positive breast cancer.

Selected References

  1. Fisher B, Costantino JP, Wickerham DL, et al. Tamoxifen for prevention of breast cancer: Report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. Journal of the National Cancer Institute 1998; 90(18):1371–1388.

  2. Fisher B, Costantino JP, Wickerham DL, et al. Tamoxifen for the prevention of breast cancer: Current status of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. Journal of the National Cancer Institute 2005; 97(22):1652–1662.

  3. Vogel VG, Costantino JP, Wickerham DL, et al. Effects of tamoxifen vs raloxifene on the risk of developing invasive breast cancer and other disease outcomes: The NSABP Study of Tamoxifen and Raloxifene (STAR) P-2 Trial. Journal of the American Medical Association 2006; 295(23):2727–2741.

  4. Winer EP, Hudis C, Burstein HJ, et al. American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer: Status report 2004. Journal of Clinical Oncology 2005; 23(3):619–629.

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Glossary Terms

abdominal
Having to do with the abdomen, which is the part of the body between the chest and the hips that contains the pancreas, stomach, intestines, liver, gallbladder, and other organs.
abnormal
Not normal. An abnormal lesion or growth may be cancer, premalignant (likely to become cancer), or benign (not cancer).
adjuvant therapy (A-joo-vant THAYR-uh-pee)
Treatment given after the primary treatment to increase the chances of a cure. Adjuvant therapy may include chemotherapy, radiation therapy, hormone therapy, or biological therapy.
anastrozole
An anticancer drug that is used to decrease estrogen production and suppress the growth of tumors that need estrogen to grow. It belongs to the family of drugs called nonsteroidal aromatase inhibitors.
antiestrogen (AN-tee-ES-truh-jin)
A substance that prevents cells from making or using estrogen (a hormone that plays a role in the formation of female sex characteristics, the menstrual cycle, and pregnancy). Antiestrogens may stop some cancer cells from growing and are used to prevent and treat breast cancer. They are also being studied in the treatment of other types of cancer. An antiestrogen is a type of hormone antagonist.
aromatase inhibitor (uh-ROH-muh-tayz in-HIH-bih-ter)
A drug that prevents the formation of estradiol, a female hormone, by interfering with an aromatase enzyme. Aromatase inhibitors are used as a type of hormone therapy for postmenopausal women who have hormone-dependent breast cancer.
blood
A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.
breast cancer (brest KAN-ser)
Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.
cancer (KAN-ser)
A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.
cell (sel)
The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.
chemotherapy (KEE-moh-THAYR-uh-pee)
Treatment with drugs that kill cancer cells.
clinical trial
A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called clinical study.
cure
To heal or restore health; a treatment to restore health.
diagnosis (DY-ug-NOH-sis)
The process of identifying a disease, such as cancer, from its signs and symptoms.
drug
Any substance, other than food, that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition. Also refers to a substance that alters mood or body function, or that can be habit-forming or addictive, especially a narcotic.
ductal carcinoma in situ (DUK-tal KAR-sih-NOH-muh in SYE-too)
A noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, ductal carcinoma in situ may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive. Also called DCIS and intraductal carcinoma.
endometrial cancer (EN-doh-MEE-tree-ul KAN-ser)
Cancer that forms in the tissue lining the uterus (the small, hollow, pear-shaped organ in a woman's pelvis in which a baby grows). Most endometrial cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids).
estrogen (ES-truh-jin)
A type of hormone made by the body that helps develop and maintain female sex characteristics and the growth of long bones. Estrogens can also be made in the laboratory. They may be used as a type of birth control and to treat symptoms of menopause, menstrual disorders, osteoporosis, and other conditions.
estrogen replacement therapy (ES-truh-jin rih-PLAYSS-munt THAYR-uh-pee)
Hormones (estrogen, progesterone, or both) given to postmenopausal women or to women who have had their ovaries surgically removed. Hormones are given to replace the estrogen no longer produced by the ovaries. Also called ERT.
exemestane (EK-seh-MEH-stayn)
A drug used to treat advanced breast cancer and to prevent recurrent breast cancer in postmenopausal women who have already been treated with tamoxifen. It is also being studied in the treatment of other types of cancer. Exemestane causes a decrease in the amount of estrogen made by the body. It is a type of aromatase inhibitor. Also called Aromasin.
fatigue
A condition marked by extreme tiredness and inability to function due lack of energy. Fatigue may be acute or chronic.
fertility (fer-TIL-i-tee)
The ability to produce children.
fetus (FEET-us)
The developing offspring from 7 to 8 weeks after conception until birth.
hormone (HOR-mone)
One of many chemicals made by glands in the body. Hormones circulate in the bloodstream and control the actions of certain cells or organs. Some hormones can also be made in the laboratory.
hormone receptor (HOR-mone reh-SEP-ter)
A cell protein that binds a specific hormone. The hormone receptor may be on the surface of the cell or inside the cell. Many changes take place in a cell after a hormone binds to its receptor.
hormone therapy (HOR-mone THAYR-uh-pee)
Treatment that adds, blocks, or removes hormones. For certain conditions (such as diabetes or menopause), hormones are given to adjust low hormone levels. To slow or stop the growth of certain cancers (such as prostate and breast cancer), synthetic hormones or other drugs may be given to block the body’s natural hormones. Sometimes surgery is needed to remove the gland that makes a certain hormone. Also called endocrine therapy, hormonal therapy, and hormone treatment.
hot flash
A sudden, temporary onset of body warmth, flushing, and sweating (often associated with menopause).
hysterectomy (HIS-teh-REK-toh-mee)
Surgery to remove the uterus and, sometimes, the cervix. When the uterus and the cervix are removed, it is called a total hysterectomy. When only the uterus is removed, it is called a partial hysterectomy.
impotence
In medicine, refers to the inability to have an erection of the penis adequate for sexual intercourse. Also called erectile dysfunction.
invasive cancer (in-VAY-siv KAN-ser)
Cancer that has spread beyond the layer of tissue in which it developed and is growing into surrounding, healthy tissues. Also called infiltrating cancer.
letrozole (LET-ruh-zole)
A drug used to treat advanced breast cancer in postmenopausal women. Letrozole causes a decrease in the amount of estrogen made by the body. It is a type of aromatase inhibitor. Also called Femara.
lobular carcinoma in situ (LAH-byuh-ler KAR-sih-NOH-muh in SY-too)
A condition in which abnormal cells are found in the lobules of the breast. Lobular carcinoma in situ seldom becomes invasive cancer; however, having it in one breast increases the risk of developing breast cancer in either breast. Also called LCIS.
menopause (MEH-nuh-PAWZ)
The time of life when a woman’s ovaries stop working and menstrual periods stop. Natural menopause usually occurs around age 50. A woman is said to be in menopause when she hasn’t had a period for 12 months in a row. Symptoms of menopause include hot flashes, mood swings, night sweats, vaginal dryness, trouble concentrating, and infertility.
menstrual cycle (MEN-stroo-al)
The monthly cycle of hormonal changes from the beginning of one menstrual period to the beginning of the next.
metastatic (meh-tuh-STA-tik)
Having to do with metastasis, which is the spread of cancer from one part of the body to another.
National Cancer Institute
The National Cancer Institute, part of the National Institutes of Health of the United States Department of Health and Human Services, is the Federal Government's principal agency for cancer research. The National Cancer Institute conducts, coordinates, and funds cancer research, training, health information dissemination, and other programs with respect to the cause, diagnosis, prevention, and treatment of cancer. Access the National Cancer Institute Web site at http://www.cancer.gov. Also called NCI.
nausea
A feeling of sickness or discomfort in the stomach that may come with an urge to vomit. Nausea is a side effect of some types of cancer therapy.
oral (OR-ul)
By or having to do with the mouth.
osteoporosis (OS-tee-oh-puh-ROH-sis)
A condition that is marked by a decrease in bone mass and density, causing bones to become fragile.
ovary (OH-vuh-ree)
One of a pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are located in the pelvis, one on each side of the uterus.
PDQ
PDQ is an online database developed and maintained by the National Cancer Institute. Designed to make the most current, credible, and accurate cancer information available to health professionals and the public, PDQ contains peer-reviewed summaries on cancer treatment, screening, prevention, genetics, complementary and alternative medicine, and supportive care; a registry of cancer clinical trials from around the world; and directories of physicians, professionals who provide genetics services, and organizations that provide cancer care. Most of this information, and more specific information about PDQ, can be found on the NCI's Web site at http://www.cancer.gov/cancertopics/pdq. Also called Physician Data Query.
pelvic
Having to do with the pelvis (the lower part of the abdomen located between the hip bones).
placebo
An inactive substance or treatment that looks the same as, and is given the same way as, an active drug or treatment being tested. The effects of the active drug or treatment are compared to the effects of the placebo.
postmenopausal (post-MEH-nuh-pawz-ul)
Having to do with the time after menopause. Menopause (“change of life”) is the time in a woman's life when menstrual periods stop permanently.
premenopausal (pree-MEH-nuh-pawz-ul)
Having to do with the time before menopause. Menopause ("change of life") is the time of life when a woman's menstrual periods stop permanently.
protein (PRO-teen)
A molecule made up of amino acids that are needed for the body to function properly. Proteins are the basis of body structures such as skin and hair and of substances such as enzymes, cytokines, and antibodies.
raloxifene (ral-OX-ih-feen)
The active ingredient in a drug used to reduce the risk of invasive breast cancer in postmenopausal women who are at high risk of the disease or who have osteoporosis. It is also used to prevent and treat osteoporosis in postmenopausal women. It is also being studied in the prevention of breast cancer in certain premenopausal women and in the prevention and treatment of other conditions. Raloxifene blocks the effects of the hormone estrogen in the breast and increases the amount of calcium in bone. It is a type of selective estrogen receptor modulator (SERM).
second primary cancer
Refers to a new primary cancer in a person with a history of cancer.
selective estrogen receptor modulator (seh-LEK-tiv ES-truh-jin reh-SEP-ter MAH-juh-lay-ter)
A drug that acts like estrogen on some tissues but blocks the effect of estrogen on other tissues. Tamoxifen and raloxifene are selective estrogen receptor modulators. Also called SERM.
side effect
A problem that occurs when treatment affects healthy tissues or organs. Some common side effects of cancer treatment are fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.
stage
The extent of a cancer in the body. Staging is usually based on the size of the tumor, whether lymph nodes contain cancer, and whether the cancer has spread from the original site to other parts of the body.
stroke
In medicine, a loss of blood flow to part of the brain, which damages brain tissue. Strokes are caused by blood clots and broken blood vessels in the brain. Symptoms include dizziness, numbness, weakness on one side of the body, and problems with talking, writing, or understanding language. The risk of stroke is increased by high blood pressure, older age, smoking, diabetes, high cholesterol, heart disease, atherosclerosis (a build-up of fatty material and plaque inside the coronary arteries), and a family history of stroke.
surgery (SER-juh-ree)
A procedure to remove or repair a part of the body or to find out whether disease is present. An operation.
symptom
An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.
tamoxifen (tuh-MOK-sih-FEN)
A drug used to treat certain types of breast cancer in women and men. It is also used to prevent breast cancer in women who have had ductal carcinoma in situ (abnormal cells in the ducts of the breast) and in women who are at a high risk of developing breast cancer. Tamoxifen is also being studied in the treatment of other types of cancer. It blocks the effects of the hormone estrogen in the breast. Tamoxifen is a type of antiestrogen. Also called tamoxifen citrate.
therapy (THAYR-uh-pee)
Treatment.
tissue (TISH-oo)
A group or layer of cells that work together to perform a specific function.
tumor (TOO-mer)
An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancer), or malignant (cancer). Also called neoplasm.
uterine cancer (YOO-teh-rin KAN-ser)
Cancer that forms in tissues of the uterus (small, hollow, pear-shaped organ in a woman's pelvis in which a baby grows). Two types of uterine cancer are endometrial cancer (cancer that begins in cells lining the uterus) and uterine sarcoma (a rare cancer that begins in muscle or other tissues in the uterus).
uterine sarcoma (YOO-teh-rin sar-KOH-muh)
A rare type of uterine cancer that forms in muscle or other tissues of the uterus (the small, hollow, pear-shaped organ in a woman's pelvis in which a baby grows). It usually occurs after menopause. The two main types are leiomyosarcoma (cancer that begins in smooth muscle cells) and endometrial stromal sarcoma (cancer that begins in connective tissue cells).
uterus (YOO-ter-us)
The small, hollow, pear-shaped organ in a woman's pelvis. This is the organ in which a baby grows. Also called womb.
vagina (vuh-JY-nuh)
The muscular canal extending from the uterus to the exterior of the body. Also called birth canal.
vomit
To eject some or all of the contents of the stomach through the mouth.


Table of Links

1http://www.cancer.gov/cancertopics/factsheet/Risk/menopausal-hormones
2http://www.cancer.gov/cancertopics/factsheet/Prevention/breast-cancer
3http://www.cancer.gov/cancertopics/factsheet/STARresultsQandA
4http://www.cancer.gov/cancertopics/types/breast
5http://www.cancer.gov/clinicaltrials/digestpage/BCPT
6http://www.cancer.gov/star
7http://www.cancer.gov/cancertopics/understandingcancer/estrogenreceptors